During manufacture of semiconductors and semiconductor microcircuits, it is frequently necessary to coat the materials from which the semiconductors and microcircuits are manufactured with a polymeric organic substance, generally referred to as a photoresist, e.g., a substance which forms an etch resist upon exposure to light. These photoresists are used to protect selected areas of the surface of the substrate, e.g. silicon, SiO.sub.2 or while such etchant selectively attacks the unprotected area of the substrate. Following completion of the etching operation and washing away of the residual etchant, it is necessary that the resist be removed from the protective surface to permit essential finishing operations.
It is necessary in a photolithographic process that the photoresist material, following pattern delineation, be evenly and completely removed from all unexposed areas, in the case of positive resists, or exposed areas in the case of negative resists, so as to permit further lithographic operations. Even the partial remains of a resist in an area to be further patterned is undesirable. Also, undesired resist residues between patterned lines can have deleterious effects on subsequent processes, such as metallization, or cause undesirable surface states and charges.
A common method used in removing the photoresist from the substrate is by contacting the substrate with an organic stripper. Heretofore these organic strippers have been composed of various components whose purpose it was to lift and remove the polymeric photoresist from the substrate. However, these stripping solutions have heretofore usually contained chlorinated hydrocarbon compounds and phenolic compounds which resulted in a distinct disadvantage due to the toxicity of these materials as well as the pollution problems arising from their disposal.
Because many of the toxic components of such stripping compositions are highly volatile and subject to unduly high evaporation rates, the stripping compositions require special human and environmental safety precautions to be taken during storage and use of said compositions.
Recently, OSHA, EPA and other similar Federal, State and Local Governmental Regulatory Agencies have advocated a shift toward use of more human and environmentally compatible stripping compositions and stripping methods that are not subject to the aforementioned drawbacks and problems.
It is also highly desirable that stripping compositions be provided that exhibit very low vapor pressure at elevated temperatures thereby significantly reducing evaporation and thus contamination of the atmosphere.
Additionally, it is highly desirable that such stripping compositions be provided that are effective and efficient stripping compositions for removal of coatings from substrates that heretofore have resisted ready removal with conventional available strippers.
It is also desirable that effective stripping compositions be provided that are not considered undesirable by regulatory agencies overseeing their production and use.
It is also most advantageous that stripping compositions be provided with the above-identified desirable characteristics which evidence synergistic stripping efficacy and stripping results not always obtainable with the additional components.
U.S. Pat. No. 3,615,827 discloses an alkaline stripping composition containing a polyalkylene glycol, ethylene glycol monophenyl ether and a phenol derivative.
U.S. Pat. No. 3,847,839 discloses an alkaline stripping composition which includes an alkoxylated furfuryl alcohol, namely, ethoxylated furfuryl alcohol and a glycol activating agent.